The invention relates to an injection unit of an injection molding machine which is arranged movable relatively to a machine base of the injection molding machine in an axial direction, wherein the injection unit comprises a base body at which a screw cylinder is arranged, wherein a screw is arranged rotatable and axially movable in the screw cylinder, wherein the screw is connected with a drive element at one of its axial ends which can rotate the screw and can also move it in an axial direction and wherein the drive element comprises a gear element which is movable in an axial direction as well as an actuator which is in engagement with the gear element and with the base body and which can perform a translational movement in an axial direction and wherein the base body is designed as a one-piece block which has a plate-shaped reception for the screw cylinder at one of its axial ends and has a plate-shaped reception for the actuator at its opposite axial end.
An injection unit of an injection molding machine according to this kind is known from DE 600 17 393 T2. Similar solutions show DE 10 2004 023 837 B3, DE 10 204 056 209 A1, DE 103 37 785 B3, DE 36 37 897 A1 and EP 0 998 380 B1. There, a compact design for the drive of a plasticizing and injection screw is obtained by designing a gear element in such a way that it can rotate the screw and can also move the screw in an axial direction. For the axial movement a spindle-nut-system is employed. The base body in which the gear element is arranged and on which also the screw cylinder is affixed is formed by two plates which are kept at a distance by arbors.
Such a design for the base body has prevailed but has also drawbacks: The base body is composed from a plurality of single parts, so a relative high expenditure in terms of manufacturing is necessary. By composing the parts, manufacturing tolerances are cumulated so that the precision of the guidance of the parts is limited which are moved translational in the direction of the longitudinal axis.
The pre-known solutions can only ensure the mounting of the spindle in the correct position to a certain degree which leads to a susceptibility of the spindles and thus to a reduced durability due to an angular misalignment which results from inclinations and bending. Especially, it was found out that the multi-part design of the base body leads to an inaccuracy by cumulating manufacturing tolerances which influences the precision of the position in a negative way of the parts which have to be supported.
As different injection molding parameters must be known for a precise and optimized controlling and feed-back-controlling respectively of the injection molding process and as especially the force which is acting on the screw in the direction of the longitudinal axis must be measured, solutions became known which try to determine the axial force in a sufficient precise way by employing a device with big expenditures what is detrimental.